Self-applied fluorides in the forms of mouth rinses and dentifrices are widely used in this country and elsewhere in the world. They have been shown to be effective in reducing tooth decay. The fluoride containing mouth rinses formulated for daily use usually contain 250 parts per million (ppm) of fluoride as sodium fluoride or stannous fluoride. The fluoride dentifrices typically contain 1000 ppm of fluoride as sodium fluoride or sodium monofluorophosphate. The carlostatic effects of both of these fluoride regimens are believed to derive from their ability to deposit fluoride on the surfaces of teeth and other tissues in the mouth. Although the deposited fluoride is labile in nature and is easily leached out of teeth and mouth tissues, the daily application of either the rinse or dentifrice can produce and maintain an elevated level of fluoride in the mouth.
U.S. Pat. No. 4,556,561 discloses solutions, gels, and substantially nonaqueous dispersions that form dicalcium phosphate dihydrate under appropriate conditions, as well as methods of their use. These compositions are useful in topically fluoridating and/or mineralizing dental tissue, such as enamel, dentin, and exposed root surfaces. The incorporated fluoride is in the form of Ca.sub.5 (PO.sub.4).sub.3 F and is more permanently retained than CaF.sub.2 and other fluoridation products.
U.S. Pat. No. 4,048,300 discloses a single dental preparation including a material containing calcium and phosphorous. The calcium/phosphorous containing component may also include fluoride. Examples of calcium/phosphorous/fluoride components include fluorapatite, fluorohydroxyapatite, apatite, calcium deficient apatite, and hydroxyapatite substituted by a fluoranion. This component is useful in a dental cream.
U.S. Pat. No. 4,080,440 discloses a method for the remineralization of tooth enamel using a two solution system. The first solution is a cationic solution containing a calcium salt and optionally a heavy metal cation. The second solution is an anionic solution containing a phosphate salt and optionally non-phosphatic anions including fluoride ions. The pH of the solutions ranges from 2 to 4 and the ratio of calcium to phosphorous ranges from 0.01 to 100. The solution, produced by mixing the two-components, is described as a "metastable" solution and requires a residence time in the mouth of from 10 seconds to about 3 minutes in order to raise the pH of the solution such that the components of the solution precipitate in the tooth resulting in enamel remineralization.
U.S. Pat. No. 4,083,955 describes a two-step process for remineralizing dental enamel. In the process, two solutions, one comprising a calcium salt, and the other solution comprising a phosphorous salt along with an optional fluoride salt, are sequentially contacted with dental enamel. The sequential solution contact results in the surface of the enamel being remineralized.
U.S. Pat. No. 4,108,980 describes a process for applying fluoride to teeth with a material having calcium and phosphate components. The dental material includes a salt which ionizes to produce fluoride ions. The formulations described in this invention are made well in advance of application to tooth surfaces.
U.S. Pat. Nos. 4,177,258 and 4,183,915 describe stable solutions for dental remineralization. The solutions include a source of calcium ions, a source of phosphate ions and a source of fluoride. The solutions also include an anti-nucleating agent consisting of diamine tetramethylenephosphonic acids having a specific formula. The anti-nucleating agent stabilizes the calcium ions and phosphorous ions and prevents them from precipitating as large, insoluble apatite crystals by absorbing onto spherical nucleated particles as they form and blocking crystal growth.
U.S. Pat. No. 4,348,381 describes solutions similar to those described in the '258 and '915 patents above. However, the anti-nucleating agent of the '381 solution is PBTA and its water soluble salts.
U.S. Pat. No. 4,397,837 describes a two-phase dental composition in which the two phases are combined when applied to teeth. The first phase of the composition includes a calcium component. The second phase includes a water soluble phosphate component and a water soluble fluoride component.
U.S. Pat. No. 4,460,565 describes a remineralizing dentifrice composition. The composition includes a calcium containing component, two fluoride components, an alkali or alkaline earth metal fluoride and an alkali metal fluorophosphate, two phosphate components, a soluble cyclic alkali metal phosphate and a soluble linear phosphate.
U.S. Pat. No. 4,532,124 describes a dental rinse. The dental rinse includes water soluble salts of fluorine, calcium and phosphorous. The composition additionally includes a substance metabolized into an alkali, such as urea, which raises the solution pH causing calcium precipitation.
U.S. Pat. Nos. 4,606,912 and 4,610,873 describe a clear, stable aqueous mouthwash free of calcium phosphate crystals. The mouthwash includes a chelating agent in combination with a calcium ion source, and a phosphate ion source. The calcium ion source consists of a component capable of providing fluoride ions. The aqueous composition contains calcium ions, phosphate ions, and fluoride ions.
U.S. Pat. No. 4,714,608 describes an aqueous dental preparation. The dental preparation includes a fluoride component in a solution having a pH less than 2. The compound can be applied to teeth either before or after the teeth are treated with calcium. This provides for the precipitation of CaF.sub.2 as a thin homogeneous layer on the tooth enamel.
U.S. Pat. No. 4,861,590 describes a sustained release fluoride in calcium composition. The composition includes MFP (monofluorophosphate) and an ionizable calcium source. Sodium fluoride may be added to the composition as desired.
U.S. Pat. No. 4,283,385 describes dentifrices containing insoluble calcium compounds utilized as abrasive dentifrices with a minor amount of EDTA or its sodium salts. Also included in this single component dentifrice is a fluoride compound, preferably sodium monofluorophosphate.
It has also been demonstrated that a 1-minute rinse application with a sodium fluoride rinse that contained 250 ppm of F deposited 0.34/.mu.g/cm.sup.2 of F, and a 1-minute brushing with a NaF dentifrice that contained 1000 ppm of F deposited 0.25 .mu.g/cm.sup.2 of F on the tooth surface. Chow, L. C. and Takagi, S. (1991): Deposition of Fluoride on Tooth Surfaces by a Two-solution Mouth Rinse in vitro. Caries Res, 25:397-401. Based on the recommended quantity for the rinse (10 ml) or for the dentifrice (1 gram) per application and the total surface area of the teeth in the mouth, it was estimated that less than 0.5% of the F in the rinse or the dentifrice is deposited on the teeth. Some of the F is also deposited in the plaque and soft tissue surfaces, but the bulk of the F contained in the rinses or dentifrices is presumably expectorated (a small fraction of F is also swallowed). A major reason for this very low yield of F retention is the lack of a reaction mechanism for the F in the rinse or dentifrice to precipitate out during the short application time.
U.S. Pat. No. 5,145,668 (Chow and Takagi) discloses a system comprised of two components (solutions or pastes) which when brought in contact, generate a rapid but controlled reaction that precipitates calcium fluoride continuously within the 1-minute time. Component A contains a soluble calcium salt (e.g., CaCl.sub.2) and a pH buffer (sodium acetate), and component B contains a complex F compound (e.g., Na.sub.2 SiF.sub.6). Each component is stable for indefinite periods in the absence of the other. When the two components are combined, hydrolysis of the complex F compound will occur, which produces sufficient amounts of free F to cause calcium fluoride precipitation. This in turn keeps the free F concentration in the mixture sufficiently low to allow continued hydrolysis of the complex F compound and precipitation of calcium fluoride. The H+ions, a byproduct of the complex F hydrolysis, are consumed by the pH buffer so that the pH of the rinse would remain near neutral. With proper concentrations of calcium and complex F in the two solutions, a significant amount of calcium fluoride can be deposited on the tooth surface within the 1-minute application time. The chemical reactions that occur in the two-component system may be described by the following equations: EQU SiF.sub.6.sup.2- +2H.sub.2 O.fwdarw.SiO.sub.2 +6F.sup.- +4 H.sup.+( 1) EQU 3 Ca.sup.2+ +6 F.sup.- .fwdarw.3 CaF.sub.2 ( 2)
The efficacy of this two-component system has been demonstrated in studies published in the scientific literature. Chow, L. C. and Takagi, S. (1991): Deposition of Fluoride on Tooth Surfaces by a Two-solution Mouth Rinse in vitro. Caries Res, 25:397-401; Chow, L. C., Takagi, S., and Shih, S. (1992): Effect of a Two-solution Fluoride Mouthrinse on Remineralization of Enamel Lesions in vitro J. Dent. Res., 77:443-447; Vogel, G. L., Mao, Y., Carey, C. M., Chow, L. C. and Takagi, S. (1992): in vivo Fluoride Concentrations Measured for Two Hours After a NaF or a New Two-solution Rinse. J. Dent. Res. 71:448-452.